Aqueous emulsions of high softening point hydrocarbon resins and process for preparing the same

ABSTRACT

An aqueous petroleum resin emulsion is realized by the slow addition of part of the water with vigorous agitation to a resin blended with up to 10 weight percent resinplast and in the presence from 3 to 10 weight percent of an emulsifier until inversion and thereafter adding the balance of the water at low agitation and thereafter cooling said emulsion to a temperature at least about 20° C. below the softening point of the mixture of emulsifier, resin and resinplast prior to terminating agitation.

This is a division of application Ser. No. 339,647, filed 1/15/82, nowU.S. Pat. No. 4,414,346.

This invention relates to emulsions of hydrocarbon resins and moreparticularly to aqueous emulsions of resins prepared from steam crackedpetroleum fractions. It is particularly useful for difficult toemulsify, relatively high softening point, non-polar petroleum resinemulsions.

BACKGROUND OF THE INVENTION

Many synthetic resins which may be formed by emulsion polymerization arewell known in the art. It is not difficult to form stable aqueousdispersions of such resins by addition of the resin feed, an appropriatedispersing agent and catalyst to water with stirring. However,emulsification of resins produced by other polymerization techniquesrequires that the bulk polymer must be dispersed in water to obtain anaqueous dispersion. Such a type is the hydrocarbon resins produced fromsteam-cracked petroleum fractions.

These hydrocarbon resins, i.e. petroleum resins, are defined herein atthe thermoplastic resins obtained by polymerization, in the presence ofa catalyst of the Friedel-Crafts type, of steam cracked petroleumdistillates, boiling in the range between about 30° C. and 280° C., orany fraction of these distillates boiling within the said range, or ofmixtures of olefins and diolefins containing sufficient diolefins toobtain a resin and not an oil. This polymerization is performed attempertures which range generally from 0° to 70° C., and preferably from30° C. to 55° C.

These resins are polydienic in character and can have a ring and ballsoftening point between about 38° C. and 180° C.

Since these resins are solid at room temperature numerous approacheshave been utilized to produce aqueous emulsions of said resins forapplication as an adhesive, as a saturant or coating for paper or clothor as a sizing or binding material in paper pulp.

One approach was to solvate the resin in hydrocarbon solvent and thencombine resin solution and water. Invariably some residual hydrocarbonsolvent remains in the finished emulsion, and this is undesirable incertain applications. This has led to the development of solvent-freedispersions (see U.S. Pat. No. 2,809,948) and emulsions (see U.S. Pat.No. 3,377,298) of petroleum resins. In both of these formulations, ionicemulsifiers have been utilized; in the former a mixture of cationic andnon-ionic surface active agents is used to achieve a resin dispersion;and, in the latter an ionic surfactant is used in combination with anaqueous gel of a swelling earth to produce an emulsion paste of apetroleum resin.

Petroleum resin emulsions containing substantial amounts of plasticizersor diluents such as linseed oil and waxes and paraffins are taught inFrench Pat. No. 1,452,875 and German Offen. No. 2014652 respectively.However, such large percentages of diluent can materially modify, notalways favorably, the properties of the base resin.

Emulsion pressure sensitive adhesives desirably should be comprised ofaqueous emulsions of tackifying resins, i.e. that resin which enhancesthe adhesive properties of an emulsion polymer system used as anadhesive. It is highly desirable that raw materials added to thetackifier resin emulsion for primarily other than tack or adhesionenhancement, e.g. plasticizers or other diluents, emulsifiers,stabilizers, etc., be kept to an absolute minimum. Such materials oftenhave an adverse effect on the functional properties, e.g. tack, adhesiveproperties, of the resin being emulsified.

For a general discussion of resin emulsions for emulsion pressuresensitive adhesive use (including its commercial aspects) see thepublished talk entitled Resin Dispersions for Water Based PressureSensitive Adhesives by Robert W. Wherry and presented at The PressureSensitive Tape Council Seminar on Water Based PSA Systems in June of1979.

This invention has for one of its objects the preparation of highlyfunctional, relatively high softening point, non-polar petroleum resinemulsions without the use of volatile solvents and employing minimalplasticizers, diluents or other products constructive in emulsificationbut potentially deleterious to the emulsion end-use.

A further object is to provide an emulsion preparation method of aninversion type for the aforementioned resins which effectively producesemulsions of small particle size and exceptional stability.

A further object is provision of aqueous dispersions of hydrocarbonresins of high shelf and mechanical stability.

A further object is to provide petroleum resins in the form of alatex-like dispersion for application as a pressure sensitive adhesive,as a saturant or coating for paper or cloth, or as a sizing or bindingmaterial in paper pulp.

SUMMARY OF THE INVENTION

It has been discovered that an aqueous emulsion of a petroleum resinhaving a ring and ball softening point of about 95° C. can be realizedwhen about 45 parts by weight of said resin is melt blended with about2.5 parts by weight of naphthenic oil and about 2.5 parts by weight ofan emulsifier comprised of a polyoxyethylene alkyl aryl ether and analkyl aryl sulfonate and thereafter admixed with about 50 weight partsof water. The aqueous resin emulsion was made possible by initiallyslowly adding and dispersing with vigorous agitation boiling water insaid melted blend of resin, naphthenic oil and emulsifier over aprescribed critical time length prior to inversion of the dispersion ofwater.

Thus in accordance with the objects of this invention there is providedan aqueous emulsion of a hydrocarbon resin having a ring and ballsoftening point of at least 85° C. comprising from 3 to 10 parts byweight of an emulsifier, from 0 to 10 parts by weight of a resinplastand from 80 to 97 parts by weight of said hydrocarbon resin and thebalance being water.

This emulsion is realized by admixture of a blend suitable for providingan aqueous emulsion of a hydrocarbon resin having a ring and ballsoftening point of at least 85° C., comprising from 3 to 10 parts byweight of an emulsifier of the class of nonionic polyoxyethylene alkylaryl ether, anionic alkyl aryl sulfonates and mixtures thereof blendedwith a mixture of from 0 to 10 parts by weight of resinplast and 80 to97 parts by weight of said hydrocarbon resin, said admixture having aring and ball softening point ranging from 75° C. to 90° C. and a 95° C.melt viscosity ranging from 20,000 to 60,000 centipoises with waterthrough a novel inversion method.

According to the invention there is also taught herein a method for theproduction of a hydrocarbon resin in water emulsion comprising thesequential steps of admixing from 3 to 10 parts by weight of anemulsifier of the class consisting of nonionic polyoxyethylene alkylaryl ether, anionic alkyl aryl sulfonate and mixtures thereof with from80 to 97 parts by weight of a molten hydrocarbon resin having a ball andring softening point in excess of 85° C. and from 0 to 10 parts byweight of a resinplast, heating said admixture to about 120° C., slowlyadding water heated to about 100° C. to said heated admixture withvigorous stirring over a critical minimum period and until inversionoccurs, adding sufficient additional water with agitation to provide anaqueous emulsion containing from 30 to 75 weight % water in the finishedemulsion and thereafter cooling to a temperature less than about 20° C.below the softening point of the mixture of emulsifier, resin andresinplast prior to terminating agitation.

DETAILED DESCRIPTION OF THE INVENTION

As earlier noted, the hydrocarbon resins emulsified according to thisinvention are preferably petroleum resins prepared by homo andcopolymerization of olefins, diolefins and aromatic components,predominantly C-5 and C-9 species, from distillates of cracked petroleumstocks. A Friedel-Crafts catalyst is typically employed. The resultingresin has an aliphatic, aromatic or mixed aliphatic/aromatic characterwith a ring and ball softening point above 85° C. The methods describedherein can also be used to emulsify lower softening point resins ofsimilar character but it is the higher softening point resins which aremore difficult to emulsify and are thus addressed here.

Broadly the hydrocarbon resins are polymerized from petroleum crackeddistillates boiling in the range of about 30° C. to 280° C. or anyfraction boiling within this range. The resins are prepared by treatingthe distillate with 0.25-2.5% of a Friedel-Crafts type catalyst such asaluminum chloride, aluminum bromide, boron trifluoride, and the like orsolutions, slurries, or complexes thereof. The reactions are conductedat temperatures in the range of 0° to 70° C., and preferably 30° C. to55° C. Residual catalyst is quenched by suitable methods such asaddition of methyl alcohol and subsequent filtration, water and/orcaustic washing. The final solution is then stripped of unreactedhydrocarbons and low molecular weight oils by vacuum or steamdistillation.

In place of the petroleum cracked distillates, the feed topolymerization may consist of mixtures of a diolefin with an olefin.Sufficient diolefin must be present and incorporated in the polymer togive a resin having a suitably high melting point instead of an oil.

For most resins a resinplast is admixed therewith which in combinationwith the resin at amounts ranging up to 10% by weight (based on totalweight excluding water), preferably at amounts ranging from 3 to 10percent by weight, adjusts the ball and ring softening point of theadmixture to within 75° C. to 90° C. The resinplast includes a widevariety of materials including petroleum oils of the paraffinic,naphthenic and aromatic types, petroleum waxes, petrolatum, lowmolecular weight polyolefins such as low molecular weight, largelyamorphous polyethylenes and similar materials. The resinplast must becompatible with the resin. By reducing the softening point and the meltviscosity of the resin, the resinplast promotes distribution of thewater in the molten resin by making the resin softer and less cohesive,and thus more amenable to water addition and formation of small waterdroplets. Finally, the resinplast acts as a compatibilizer, making theresin more receptive to the emulsifier. An example of a preferredresinplast are naphthenic oils having a viscosity range of from 500 to2000 SSU (at 100° F.).

The emulsifiers which have been found useful for producing the emulsionsof the invention are a combination of a nonionic emulsifier with ananionic emulsifier. The nonionic emulsifier, for example, can be anethoxylated alkyl phenol in which the alkyl group contains from 8 to 12,preferably about 9 carbon atoms. The molar ratio of ethylene oxide toalkylphenol is selected based on the chemistry of the particular resin.Suitable anionic emulsifiers are the alkyl aryl sulphonates which aregenerally the alkali metal salts to make them water solule. Highlyuseful for the practice of this invention is the sodium or calcium saltof dodecylbenzene sulfonic acid. In total amount as already indicated,the emulsifier ranges in weight from 3% to 10%, preferably 4% to 6%, byweight.

Thus, in summary the non-water portion of the emulsion will have aconcentration range of: resin ranging from 80% to 97% by weight;emulsifier ranging from 3% to 10%; resinplast ranging from 0 to 10%. Thewater content of the finished emulsion will range from 30 to 75 weight%.

Any non-reactive additives may be used in the emulsion of thisinvention, for example, pigments, dyes and labeling agents.

This invention also contemplates a method for the production of ahydrocarbon solid in water emulsion comprising the sequential steps ofadmixing, preferably by shearing agitation, from 3 to 10 parts by weightof an emulsifier preferably consisting of nonionic polyoxyethylene alkylaryl ether, anionic alkyl aryl sulfonate and mixtures thereof, with from80 to 97 parts by weight of a molten hydrocarbon, preferably petroleum,resin having a ring and ball softening point in excess of 85° C. andfrom 0 to 10 parts by weight of a resinplast, heating said admixture toabout 120° C., slowly adding water heated to about 100° C. to saidheated admixtures with vigorous, high shear agitation over a timeperiod, the length of which is critical, until inversion occurs, addingsufficient additional water with agitation to provide an aqueousemulsion containing from 30 to 75 weight % water and thereafter coolingto a temperature less than about 20° C. below the softening point of themixture of emulsifier, resin and resinplast prior to terminatingagitation. Finished emulsion is then typically strained using cheesecloth or a commercial filter bag or filter pack.

As is indicated above, the water is dispersed in the resin admixture toform a water in oil emulsion using vigorous shearing agitation. Theimpeller design should maximize the portion of the mixing energydissipation into the emulsion which is classified as shear. Variousturbine impellers such as flat blade and disk type flat blade turbinesand high shear proprietary design impellers such as the Fawcett mixedflow impeller are suitable.

In the mixing procedure which has been detailed above, there appear tobe certain critical aspects to this procedure which are hereinafterindicated. The mixing procedure involves, as indicated, the heating ofthe resin to a molten state and blending with the resinplast if used.Thereafter the emulsifier is added to the molten resin at a temperatureof approximately 105° C. This molten mix must be blended thoroughly toassure homogeneity. During this blending the admixture temperature isincreased somewhat after which water at approximately 100° C. is meteredinto the admixture. Water addition can tend to reduce the temperature ofthe mixture. It is imperative that the temperature remain above thesoftening point of the resin-resinplast-emulsifier softening point,typically a minimum of 5° C. to 10° C. above, at all times prior toinversion. Further, impeller rotational speed must be high (e.g. 550-700rpm in a one liter laboratory unit) to ensure that the molten resinsurface is continously agitated and folded into the mix. During thistime a water in oil emulsion is being obtained.

When approximately 1/3 of the water addition is complete, it is highlydesirable to terminate water addition for from 5 to 10 minutes whilecontinuing vigorous agitation. It is essential that the critical timeinterval from first water addition to inversion be governed by shortlapses in water addition in this manner. Such lapses are also useful tomaintain mix temperature, the importance of which was emphasized in theparagraph above.

Mention has been made of the criticality of the time interval from firstwater addition to the point of emulsion inversion from water in oil tooil in water. Laboratory and plant data indicate that for a given resinthere is a mix time minimum, below which final resin emulsion particlesize will be undesirably large. This critical mix time is dependent uponthe power input to the mixture per unit volume of emulsion. Power inputis directly related to impeller diameter and impeller rotational speed.This critical time interval can range from approximately 20 to 30minutes in a small laboratory batch prepared employing theaforementioned very high impeller speeds to 2 plus hours in larger,plant units. It is within the skill of the art to determine the criticaltime and agitation requirement here for particular cases.

Following inversion it is desirable to reduce the vigorous nature of thestirring to a slow stirring to minimize foam and to terminate batchheating. Water should now be added to the emulsion mix at a temperaturematerially reduced below boiling and continued until the desired solidslevel is obtained. The stirring is continued at ambient temperatures forfrom 5 to 10 minutes after completion of the water addition. Prior toterminating the stirring, the emulsion temperature must be reduced to atemperature of at least 20° C. below the resin-resinplast-emulsifiersoftening point in order to prevent particle size growth or skindevelopment in the emulsion system.

The aforementioned critical steps are vital to achieve excellent lowparticle size and the exceptional, unique stability exhibited by thesehydrocarbon resin emulsions.

The example set forth below illustrates several embodiments of theinvention and are not to be construed as limiting in any manner.

EXAMPLE 1

85 parts by weight of a non-polar, 93° C. softening point petroleumresin, Escorez 2101 sold by Exxon Chemical Americas, Houston, Tex. isheated to a temperature of about 115° C. and admixed with 10 weightparts of naphthenic oil and 5 weight parts of Atlox 3404 F emulsifiersold by ICI Americas Inc. The Atlox 3404 F is reported to be a blend ofpolyoxyethylene alkyl aryl ether and alky aryl sulfonate. The moltenresin is blended with the naphthenic oil, then the emulsifier is stirredinto the resin-resinplast blend until a complete and thorough blend ofall three ingredients is achieved. The resin-resinplast-emulsiferadmixed blend is heated at approximately 120° C. at which time the firstthird of water is metered in at a temperature of approximately 100° C.Actual water addition will exceed 1/3 to make up for water evaporation.The metering in continues with fast blending speed, i.e. 550-700 rpm, soas to make certain that the resin admixture is continuously agitated andthat the water is folded into the mix. The temperature during thisinitial metering is kept at about 88°-93° C. in order to maintain aviscosity at appropriate levels to facilitate the mixing. Whenapproximately 1/3 of the water has been added, the system is mixedvigorously for 5 to 10 minutes after which the hot water addition isresumed while maintaining the temperature of the system at about 88°-93°C. Several additional, spaced water addition shutdowns are utilized toprolong mixing and control batch temperature. Hot water continues untilinversion occurs at which time the heat supplied to the system isterminated. The balance of the water is added at ambient temperature andthe stirrer speed is reduced to minimize foam. Water addition continueswith low stirring and upon its completion stirring continues from 5 to10 minutes. Prior to terminating agitation it is necessary to cool themixture to approximately 20° C. below to the ring and ball softeningpoint of the mixture of resin-resinplast-emulsifier or to about 60° C.Upon terminating agitation the resin emulsion is passed through a cheesecloth so as to remove any large flakes of dried particles. In alaboratory mix typical times are as follows: resin melting and blendingof resinplast and emulsifier--30 to 45 minutes, water addition to theinversion point--20 to 45 minutes, final dilution and cooling--about 15minutes.

The resulting emulsion is slightly off-white in color, smooth, notgritty to the touch, dries to a very fine powder on the finger tips andwill not separate even after months of shelf storage (unagitated).Particle sizes averaging 0.5 micron have been achieved which makes suchemulsions excellent components for emulsion adhesives.

EXAMPLE 2

90 parts by weight of a non-polar, 94° C. softening point petroleumresin, Escorez 1310 sold by Exxon Chemical Americas, Houston, Tex., isheated to a temperature of about 115° C. and admixed with 5 weight partsof naphthenic oil and 5 weight parts of Atlox 3404 F emulsifier sold byICI Americas, Inc. Emulsion preparation procedures follow the samecourse as in Example 1. The resulting emulsion is white in color butotherwise similar to that in Example 1 in appearance, feel andproperties. This emulsion, too, is an excellent component for use inwater based adhesives.

As is apparent from the foregoing description, the emulsion preparationprocedure has the advantage that does not require either reduction orincrease in pressure to achieve the emulsion, i.e. the emulsion can becarried out at normal atmospheric pressure.

It will be apparent from the foregoing that, while predicted forms ofthe invention have been illustrated and described, various modificationscan be made without parting from the spirit and scope of the invention.Accordingly it is not intended that the invention be limited except bythe appended claims.

What is claimed is:
 1. A method for the production of a hydrocarbonresin in water emulsion comprising the sequential steps of admixing from3 to 10 parts by weight of an emulsifier of the class consisting ofnonionic polyoxyethylene alkyl aryl ether, anionic alkyl aryl sulfonateand mixtures thereof with from 80 to 97 parts by weight resin having aball and ring softening point in excess of 85° C. and from 0 to 10 partsby weight of a resinplast, heating said admixture to about 120° C.,slowly adding water heated to about 100° C. to said heated admixturewith stirring over a period of at least 20 minutes and until inversionoccurs, and then adding sufficient additional water with agitation toprovide an aqueous emulsion containing from 30 to 75 weight % water andthereafter cooling to a temperature less than about 20° C. below thesoftening point of the mixture of emulsifier, resin and resinplast priorto terminating agitation.
 2. A method according to claim 1 wherein saidstirring is vigorous agitation and the temperature of said admixture isat least 5° C.-10° C. greater than its softening point prior toinversion.